/*
 * [The "BSD licence"]
 * Copyright (c) 2005-2008 Terence Parr
 * All rights reserved.
 *
 * Conversion to C#:
 * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

namespace Antlr.Runtime
{

    /** <summary>
     *  A simple stream of integers used when all I care about is the char
     *  or token type sequence (such as interpretation).
     *  </summary>
     */
    public interface IIntStream
    {
        void Consume();

        /** <summary>
         *  Get int at current input pointer + i ahead where i=1 is next int.
         *  Negative indexes are allowed.  LA(-1) is previous token (token
         *  just matched).  LA(-i) where i is before first token should
         *  yield -1, invalid char / EOF.
         *  </summary>
         */
        int LA( int i );

        /** <summary>
         *  Tell the stream to start buffering if it hasn't already.  Return
         *  current input position, Index, or some other marker so that
         *  when passed to rewind() you get back to the same spot.
         *  rewind(mark()) should not affect the input cursor.  The Lexer
         *  track line/col info as well as input index so its markers are
         *  not pure input indexes.  Same for tree node streams.
         *  </summary>
         */
        int Mark();

        /** <summary>
         *  Return the current input symbol index 0..n where n indicates the
         *  last symbol has been read.  The index is the symbol about to be
         *  read not the most recently read symbol.
         *  </summary>
         */
        int Index
        {
            get;
        }

        /** <summary>
         *  Reset the stream so that next call to index would return marker.
         *  The marker will usually be Index but it doesn't have to be.  It's
         *  just a marker to indicate what state the stream was in.  This is
         *  essentially calling release() and seek().  If there are markers
         *  created after this marker argument, this routine must unroll them
         *  like a stack.  Assume the state the stream was in when this marker
         *  was created.
         *  </summary>
         */
        void Rewind( int marker );

        /** <summary>
         *  Rewind to the input position of the last marker.
         *  Used currently only after a cyclic DFA and just
         *  before starting a sem/syn predicate to get the
         *  input position back to the start of the decision.
         *  Do not "pop" the marker off the state.  mark(i)
         *  and rewind(i) should balance still. It is
         *  like invoking rewind(last marker) but it should not "pop"
         *  the marker off.  It's like seek(last marker's input position).
         *  </summary>
         */
        void Rewind();

        /** <summary>
         *  You may want to commit to a backtrack but don't want to force the
         *  stream to keep bookkeeping objects around for a marker that is
         *  no longer necessary.  This will have the same behavior as
         *  rewind() except it releases resources without the backward seek.
         *  This must throw away resources for all markers back to the marker
         *  argument.  So if you're nested 5 levels of mark(), and then release(2)
         *  you have to release resources for depths 2..5.
         *  </summary>
         */
        void Release( int marker );

        /** <summary>
         *  Set the input cursor to the position indicated by index.  This is
         *  normally used to seek ahead in the input stream.  No buffering is
         *  required to do this unless you know your stream will use seek to
         *  move backwards such as when backtracking.
         *  </summary>
         *
         *  <remarks>
         *  This is different from rewind in its multi-directional
         *  requirement and in that its argument is strictly an input cursor (index).
         *
         *  For char streams, seeking forward must update the stream state such
         *  as line number.  For seeking backwards, you will be presumably
         *  backtracking using the mark/rewind mechanism that restores state and
         *  so this method does not need to update state when seeking backwards.
         *
         *  Currently, this method is only used for efficient backtracking using
         *  memoization, but in the future it may be used for incremental parsing.
         *
         *  The index is 0..n-1.  A seek to position i means that LA(1) will
         *  return the ith symbol.  So, seeking to 0 means LA(1) will return the
         *  first element in the stream. 
         *  </remarks>
         */
        void Seek( int index );

        /** <summary>
         *  Only makes sense for streams that buffer everything up probably, but
         *  might be useful to display the entire stream or for testing.  This
         *  value includes a single EOF.
         *  </summary>
         */
        int Count
        {
            get;
        }

        /** <summary>
         *  Where are you getting symbols from?  Normally, implementations will
         *  pass the buck all the way to the lexer who can ask its input stream
         *  for the file name or whatever.
         *  </summary>
         */
        string SourceName
        {
            get;
        }
    }
}
